2013/11/17 Nick Williams <nicho...@nicholaswilliams.net>:
> I have an EL 3.0 edge case that I need help understanding. Am I doing
> something wrong (I don't think so) or is the Tomcat 8.0 implementation
> missing something?
>
> Consider the following EL expression:
>
> ${users.stream()
> .filter(u -> fn:contains(u.username, '1'))
> .sorted((u1, u2) -> u1.lastName.compareTo(u2.lastName) == 0 ?
> u1.firstName.compareTo(u2.firstName) : u1.lastName.compareTo(u2.lastName))
> .toList()}
>
> This works as expected. However, it results in potentially evaluating
> u1.lastName.compareTo(u2.lastName) twice. My understanding is that the
> right-hand side of a lambda expression can be any valid EL expression, so I
> believe this should also work:
>
> ${users.stream()
> .filter(u -> fn:contains(u.username, '1'))
> .sorted((u1, u2) -> x = u1.lastName.compareTo(u2.lastName); x
> == 0 ? u1.firstName.compareTo(u2.firstName) : x)
> .toList()}
>
> However, this doesn't evaluate. I get the following error instead:
>
> org.apache.el.parser.ParseException: Encountered " "=" "= "" at line 3,
> column 38.
> Was expecting one of:
> "." ...
> ")" ...
> etc ...
>
What if you add "(" ")" ?
What operator has higher priority, "->" or ";" ?
> Next I tried to reduce the properties present in each user using the stream
> "map" method. Once again, with the understanding that the right-hand side of
> a lambda expression can be any valid EL expression, I use an EL Map literal
> to construct a reduced set of properties:
>
> ${users.stream()
> .filter(u -> fn:contains(u.username, '1'))
> .map(u -> {'username':u.username, 'first':u.firstName,
> 'last':u.lastName})
> .sorted((u1, u2) -> u1.lastName.compareTo(u2.lastName) == 0 ?
> u1.firstName.compareTo(u2.firstName) : u1.lastName.compareTo(u2.lastName))
> .toList()}
>
> However, that doesn't work and I get this error:
>
> org.apache.el.parser.ParseException: Encountered "<EOF>" at line 3, column 88.
> Was expecting one of:
> "." ...
> ")" ...
> etc ...
>
I do not understand the above. Can you provide a simple test case?
Which one of the expressions does not work? Can you remove the others?
> Section 2.3.6.4 of the specification uses the following example, where a LIST
> literal is used as the right-hand side of the mapping lambda expression:
>
> products.stream().filter(p->p.unitPrice >= 10).
> .map(p->[p.name, p.unitPrice])
> .toList()
>
> I tried to use this exact syntax, as shown in the spec, with my example:
>
> ${users.stream()
> .filter(u -> fn:contains(u.username, '1'))
> .map(u -> [u.username, u.firstName, u.lastName])
> .sorted((u1, u2) -> u1.lastName.compareTo(u2.lastName) == 0 ?
> u1.firstName.compareTo(u2.firstName) : u1.lastName.compareTo(u2.lastName))
> .toList()}
>
> And now I get this lovely error:
>
> javax.el.ELException: java.lang.NumberFormatException: For input string:
> "lastName"
> javax.el.BeanELResolver.invoke(BeanELResolver.java:185)
>
> org.apache.jasper.el.JasperELResolver.invoke(JasperELResolver.java:147)
> org.apache.el.parser.AstValue.getValue(AstValue.java:158)
> ...
>
> I'm sure I'm doing something wrong here, but I'm not exactly sure what. On
> the other hand, it's possible that the Tomcat 8.0 implementation is just
> wrong. Can someone shed some light on this?
>
Best regards,
Konstantin Kolinko
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